Tube-type heat exchangers are extensively utilized, and these heat exchangers normally employ a large number of tubes connected in series and disposed in adjacent parallel relationships. The adjacent tubes are connected by end fittings which are commonly referred to as hairpins. To facilitate the forming of hairpins and similar such fittings, various machines have been developed which permit tubular stock to be withdrawn from a supply coil, following which the free end of the tubular stock is formed into the desired shape and is severed from the stock which remains connected to the coil. The known apparatus capable of forming such hairpins have typically permitted the simultaneous forming of several identical fittings during each forming operation, and hence have required the use of a coil stand disposed adjacent the input end of the apparatus, which coil stand typically supports several identical coils of tubing thereon. The coils are individually supported for rotation substantially about horizontal axes, whereby tubing is unwound from all of the coils and fed into the forming apparatus during each cycle to permit the simultaneous formation of a plurality of identical hairpins or like fittings. The forming apparatus typically has a drive device associated therewith which intermittently grips the plurality of tubes to feed a selected length thereof into and through the apparatus. The coils are thus intermittently rotatably moved in a steplike manner to intermittently feed tubing to the apparatus. With this arrangement, however, the coils have necessarily been limited with respect to their maximum size in order to permit the coils to be intermittently rotated and stopped in a steplike manner consistent with the driving and production capability of the forming apparatus. This has hence limited the capability of the apparatus, particularly with respect to the usable size of coils, since the excessive inertia of large coils has prevented them from being successfully utilized due to the difficulty of both initiating and stopping rotation. Reference is made to earlier U.S. Pat. Nos. 3 568 488 and 4 085 608, as owned by the assignee of this application, the disclosures of which are incorporated herein by reference. These earlier patents disclose known apparatus for forming hairpins, which apparatus utilized coil stands for supporting a plurality of tubing coils which individually feed tubing to the apparatus.
Since earlier forming apparatus have normally relied upon friction belts or releasable clamps for intermittently engaging and advancing the tubing, this has hence limited the capacity and capability of the apparatus. For example, when the tubing coil becomes large, it is difficult for the known apparatus to properly initiate rotation of the coil to effect unwinding of the tubing. In some instances, there has been insufficient slippage so that excessive strain is imposed on the tubing. In other instances, this has resulted in excessive slippage between the tubing and the driving device so that improper feeding of the tubing results. Alternately, the operational or production rate of the apparatus has been reduced to a magnitude consistent with the capability of the apparatus to intermittently withdraw the tubing from the coil. At the same time, difficulties have been encountered with the prior apparatus in terms of stopping the coil after the desired amount of tubing has been unwound since, particularly when the coil is large, the inertia of the rotating coil makes stoppage of same difficult so that excessive unwinding is commonly encountered.
Accordingly, it is an object of the present invention to provide an improved stand for supporting a plurality of tubing coils, which stand has power-assist units for drivingly engaging the coil spools to at least assist the initial start-up rotation thereof when tubing is to be unwound therefrom. This improved stand preferably has a braking system associated therewith for engaging the coil spools to stop same so that proper unwinding and feeding of tubing from the coil to the forming apparatus can be accurately and precisely controlled in accordance with the desired mode of operation and production rate of the forming apparatus. The improved coil stand of this invention hence overcomes many of the disadvantages associated with the known structures of this type.
Another object of the invention is to provide an improved coil stand, as aforesaid, which permits the utilization of coils of substantially increased size, while at the same time permitting efficient starting and stopping of the coils so as to permit intermittent unwinding and feeding of tubing to a forming apparatus, whereby the stepwise rotation of the coil can be properly synchronized with the operational cycle of the forming apparatus in such manner as to permit the forming apparatus to operate in an efficient and highly productive manner. Since this improved stand permits the use of substantially larger coils, the forming apparatus can be maintained in substantially continuous operation for greatly increased periods of time, whereby costly and time consuming shut-downs caused by the necessity of having to replace empty coil spools can hence be greatly minimized.
In the present invention, there is provided a stand or frame having a plurality of upright supports or posts each provided with a substantially horizontal axle, and each of these axles is adapted to rotatably support one or more spools each containing a coil of tubing therearound. The stand is positionally related to the input end of a forming apparatus, such as the apparatus disclosed in U.S. Pat. No. 3 568 488, so that a plurality of side-by-side tubes can be simultaneously fed into the apparatus in an intermittent steplike manner to permit a selected length of tubing to be appropriately formed and severed from the remaining tubing. An intermittent reciprocal drive device is mounted on the stand for cooperative engagement with a respective spool, which drive device in the preferred embodiment includes a reciprocal driving element having a driving pin or lug which is engageable with one of a series of openings or recesses formed in an end flange on the respective spool. When the forming apparatus signals for the advancement of the tubing, the drive device is energized so that the drive lug engages the spool and provides a power-assist to initiate the rotation of the spool in an unwinding direction, following which the drive lug automatically disengages the spool so that it can continue to rotate and hence unwind the desired length of tubing therefrom. When the desired length of tubing has been fed into the forming apparatus, as determined by the separate driving means associated therewith, the forming apparatus then transmits a stop signal to the stand for energizing a brake which engages the spool so as to stop rotation thereof. At a selected time, the reciprocal drive device is returned to its initial position, and during this return the drive lug again momentarily engages and reversely rotates the spool a selected angular extent, which limited reverse rotation is sufficient to eliminate or minimize the slack in the tubing which extends from the spool to the forming apparatus. Successive operational cycles can be automatically and efficiently performed, with each operational cycle involving the same series of engagements and movements.
Other objects and purposes of the invention will be apparent to persons familiar with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.